Silicon is a highly promising anode material for the next generation of lithium ion batteries, since it has a very high specific capacity of 4200 mAh/g (at 0.4 V against lithium), which is approximately eleven times higher than the specific capacity of graphite, which is 372 mAh/g. In addition, silicon is non-toxic and readily available.
However, presently silicon anodes still have a few limitations.
On the one hand, silicon has a low electrical conductivity; therefore, silicon anodes are ill suited for high-power applications.
On the other hand, silicon as an anode material in lithium ion batteries is subject to great volume fluctuations during the battery cycle. For example, lithium is embedded into silicon while the battery is charged, and forms an alloy, for example, according to the reaction Si+4.4 Li→Li4.4Si, resulting inconsiderable expansion of the silicon volume. During discharge, lithium is released again, resulting in the silicon volume being considerably reduced again. As a result, when silicon particles are simply physically mixed with carbon particles, for example, for increasing the electrical conductivity, both particle-particle contacts and particle-current collector contacts are interrupted during the cycle, whereby the capacity of the silicon anode is considerably reduced during multiple cycles, which impairs cycle stability.
U.S. Patent Application Publication US 2010/0193731 A1 describes a composite anode material, which is manufactured with the aid of sintering and contains metal particles and carbon nanotubes covalently bonded to the metal particles.
U.S. Patent Application Publication US 2012/0107693 A1 describes an anode material for a lithium battery, which is manufactured with the aid of sputtering and includes a silicon-containing compound having the general formula SiCx with 0.05≤x≤1.5.